The applicants proposed a two-phase research program aimed at developing compact, portable near-infrared (NIR)-tunable solid-state lasers for tissue welding and developing better understanding of the laser tissue fusion mechanism. The specific aims of the proposed research will be: (1) development of NIR-tunable solid-state lasers to carry out laser tissue welding; and (2) study of the laser tissue welding using tunable lasers in animal skin and internal tissues to determine the effect of wavelength, average power, pulse duration, peak power, penetration depth, and tissue optical characteristics on the efficacy of the fusion process. The research will be focused on developing and testing compact, portable NIR tunable solid-state lasers based on well known laser crystals cr:forsterite, Cr:Ca2GeO4 and a new promising crystal Cr:LiInGeO4 filling the void around 1300 nm, for tissue welding developing better understanding of the laser tissue fusion mechanism. The laser-development effort will provide compact and reliable lasers with optimal characteristics for clinical tissue welding applications.